This Batmobile was/is a prototype when he had deals with the military. The movie is called "Batman Begins" because this was before everything. This was the very first batmobile. This was before all the fancy shit. This was before "cool gizmos".
The movie takes place right when he becomes "Batman" and was either going to go "good" or "bad"...
His "slick and rounded" batmobile comes when he his set in his ways and knows what he wants.
/nerd off